Nebulizer apparatus and method

ABSTRACT

A nebulizer for efficiently and reliably delivering aerosolized fluid to an inhaling patient is disclosed. The nebulizer includes a fixed diverter and a movable fluid orifice or fluid pathway connected with an actuator for responding to an inhalation or a manual actuation and beginning the nebulization process. Also provided is a method of providing nebulization including the steps of moving a fluid orifice or fluid pathway connected to an actuator so that the fluid orifice or fluid pathway reaches a nebulizing position during inhalation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/101,554, filed Mar. 19, 2002, now U.S. Pat. No. 6,929,003, whichclaims the benefit of provisional application Ser. No. 60/277,482, filedMar. 20, 2001, wherein the entire disclosure of each of theseapplications is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for generatingan aerosol for delivery to a patient. More particularly, the presentinvention relates to a nebulizer configured to nebulize a fluid into anaerosol in coordination with a patient's breathing.

BACKGROUND

Medical nebulizers that nebulize a fluid into an aerosol for inhalationby a patient are well-known devices commonly used for the treatment ofcertain conditions and diseases. Nebulizers have applications forconscious, spontaneously-breathing patients and for controlled,ventilated patients.

In some nebulizers, a gas and a fluid are mixed together and directedagainst a baffle or diverter. In some other nebulizers, interaction ofthe gas and fluid is enhanced through impacting the gas and fluidagainst a diverter. The term diverter, as used in this specification,includes any baffle or impinger. As a result of either nebulizationprocess described above, the fluid is transformed into an aerosol, thatis, the fluid is caused to form small particles that are suspended inthe air and that have a particle size in a range suitable for deliveryto a targeted area of a patient's respiratory tract. One way to mix thegas and fluid together in a nebulizer is to pass a quickly moving gasover a fluid orifice tip of a tube. The negative pressure created by theflow of pressurized gas is a factor that contributes to drawing fluidout of the fluid orifice into the stream of gas and nebulizing it.

Important considerations in the design of a nebulizer are the timing anddosage regulation of the aerosolized fluid. In some nebulizer designs, acontinuous stream of pressurized gas entrains the fluid against thediverter to constantly generate an aerosol until the fluid in areservoir is depleted. Continuous nebulization may result in a waste ofaerosol during a patient's exhalation or during a delay betweeninhalation and exhalation. The amount of wasted aerosol may be difficultto quantify and some of the aerosol may be lost to condensation on thenebulizer or mouthpiece during periods of non-inhalation. Nebulizersimplementing a timed or non-continuous nebulization may adversely affectparticle size and density as the nebulization is turned on and off.

Effective and economical nebulizer therapy includes the ability toquickly generate a large amount of aerosol within a predeterminedparticle size range. An effective nebulizer preferably provides thesefeatures synchronously with the inhalation of the patient. In order toactuate a mechanical nebulizer, a patient's inhalation effort mustovercome certain variables. Depending on the structural configuration ofthe nebulizer, these variables may include one or more of the following:the volumetric flow rate of the flowing gas; air leaks in the device;the force exerted by the flowing gas on a moveable diverter; and thefriction between moveable parts. The greater the flow rate, air leaksand friction, the greater the inhalation effort required in order toactuate the device. It is desirable that a nebulizer have adequatesensitivity to quickly respond to an inhalation while not adverselyrestricting the patient's inhalation.

BRIEF SUMMARY

In order to address the deficiencies in the prior art and provideimproved performance, a nebulizer and method are provided. According toa first aspect of the invention, a nebulizer is provided with a housinghaving an ambient air inlet and a chamber for holding an aerosol. An airoutlet communicates with the chamber for permitting the aerosol to bewithdrawn from the chamber. A fluid outlet and a pressurized gas outletare in communication with the chamber where the pressurized gas outletis located adjacent to the fluid outlet. In one preferred embodiment,the fluid outlet is preferably positioned at the opposite end of anozzle cover from a fluid inlet, wherein the fluid inlet is capable offluid communication with a reservoir. A diverter is positioned in thechamber in a fixed position relative to the pressurized gas orifice.

At least one portion of the fluid orifice is adjustable between anebulizing position and a non-nebulizing position. As used in thisspecification, the term “fluid orifice” means either the fluid inlet orthe fluid outlet and may be used interchangeably with these terms. Thenebulizer may have an actuator piston connected with at least a portionof a nozzle cover to move all or part of the fluid orifice, or all orpart of the fluid pathway between the reservoir of fluid and the fluidorifice. Additionally, a relief piston independently movable withrespect to the actuator piston may be used to alleviate inhalationeffort after an initial period of inhalation. In one embodiment, thefluid orifice is movable in response to a patient's breathing. Inanother embodiment, the fluid orifice is movable by moving a mechanicalactuator by hand. In yet further embodiments, the diverter may bemovable relative to the nebulizer housing, but fixedly positionedrelative to either the pressurized gas orifice or fluid orifice.

According to another aspect of the invention, a method of providing anebulized fluid to a patient includes providing a nebulizer having adiverter fixedly positioned with respect to a pressurized gas outlet ina chamber, a fluid reservoir in communication with the chamber, and anadjustable fluid pathway movably positioned to communicate fluid in thefluid reservoir with a fluid orifice in response to inhalation by thepatient. Upon inhalation through an air outlet connected to the chamber,a position of the fluid pathway is adjusted with the force of theinhalation such that the fluid in the chamber is nebulized.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an elevational side view of a nebulizer according to oneembodiment of the present invention.

FIG. 2 is an exploded top perspective view of the nebulizer of FIG. 1.

FIG. 3 is an exploded bottom perspective view of the nebulizer of FIG.1.

FIG. 4 is a bottom perspective view of a nozzle cover suitable for usein the nebulizer of FIG. 1.

FIG. 5 is a cross-sectional view of the nozzle cover of FIG. 4.

FIG. 6 is a cross-sectional view of the nebulizer of FIGS. 1–3 in anon-actuated position.

FIG. 7 is a cross-sectional view of the nebulizer of FIG. 6 in a fullyactuated position.

FIG. 8 is a cross-sectional view of the nebulizer of FIG. 1 illustratingair flow in a fully actuated position.

FIG. 9 is a cross-sectional view of an alternative embodiment of adiverter arrangement suitable for use with the nebulizer of FIG. 1.

FIG. 10 is a cross-sectional view of a second alternative embodiment ofa diverter arrangement suitable for use with the nebulizer of FIG. 1.

FIG. 11 is a cross-sectional view of a third alternative embodiment of adiverter arrangement suitable for use with the nebulizer of FIG. 1.

FIG. 12 is a partial cross-sectional view of an alternative embodimentof the nebulizer of FIGS. 1–8 in an actuated position.

FIG. 13 is a partial cross-sectional view of the nebulizer of FIG. 12 ina non-actuated position.

FIG. 14 is an exploded side elevational view of a second alternativeembodiment of the nebulizer of FIGS. 1–8.

FIG. 15 is a partial cross-sectional view of the nebulizer of FIG. 14 inan actuated position.

FIG. 16 is a partial cross-sectional view of the nebulizer of FIGS.14–15 in a non-actuated position.

FIG. 17 is a cross-sectional view of a third alternative embodiment ofthe nebulizer of FIGS. 1–8 in a non-actuated position.

FIG. 18 is a partial cross-sectional view of the nebulizer of FIG. 17 inan actuated position.

FIG. 19 is an alternative nozzle cover and vane assembly, in anon-actuated position, for use in the nebulizer of FIGS. 17–18.

FIG. 20 is an alternative nozzle cover and vane assembly, in an actuatedposition, for use in the nebulizer of FIGS. 17–18.

FIG. 21 is an exploded view of a fourth alternative embodiment of thenebulizer of FIGS. 1–8.

FIG. 22 is a cross-sectional view of the nebulizer of FIG. 21 in anon-actuated position.

FIG. 23 is a cross-sectional view of the nebulizer of FIG. 21 in anactuated position.

FIG. 24 is a sectional view of the nebulizer of FIGS. 21–23.

FIG. 25 is a lid and relief piston assembly suitable for use in thenebulizer of FIG. 21.

FIG. 26 is an alternative lid and relief piston assembly for use in thenebulizer of FIG. 21.

FIG. 27 is a cross-sectional view of a nebulizer illustrating a lockinglever.

FIG. 28 is a sectional view of the nozzle and nozzle cover of FIG. 23.

FIG. 29 is a sectional view of the nozzle and nozzle cover of FIG. 22.

FIG. 30 is a cross-sectional view of an alternative embodiment of thenebulizer of FIGS. 21–24 with a gas nozzle and nozzle cover arranged ininternal mixing configuration.

FIG. 31 is a sectional view of the gas nozzle and nozzle cover in thenebulizer of FIG. 30 in an actuated position.

FIG. 32 is a sectional view of the gas nozzle and nozzle cover in thenebulizer of FIG. 30 in a non-actuated position.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

A preferred embodiment of a nebulizer 10 for nebulizing a fluid is shownin FIGS. 1–3. As used in this specification, the term “fluid” includes,without limitation, a fluid comprising a medicine, whether in the formof an emulsion, suspension or solution, that can be nebulized into anaerosol. The embodiment of FIGS. 1–3 comprises a lid 11 attached to ahousing 13 having a top portion 12, a cylindrical middle portion 14, anda bottom portion 16. An air outlet 18 extends from the cylindricalmiddle portion 14 of the housing 13. The air outlet 18 communicates withair in the chamber 20, defined by the inside of the cylindrical middleportion 14 of the housing, and is suited to receive a mouthpiece. In apreferred embodiment, the component parts of the housing may be formedof separate, multiple pieces of material that are connected together bywelding, adhesives, threading, connector tabs. In an alternativeembodiment the housing may be constructed of a single piece of materialformed by an injection molding process. The housing may be constructedfrom a plastic material, such as polypropylene, polycarbonate or apolycarbonate blend, or a metal material. Any number of types of plasticor metal may be used to construct these parts of the nebulizer.

Referring to FIGS. 1–7, a pressurized gas inlet 22 extends into thechamber 20 through the bottom portion 16 of the housing. The opening 24of the pressurized gas inlet 22 is designed to connect with a standardvinyl gas hose. Inside the chamber 20, the pressurized gas inlet 22forms a nozzle 26 that tapers down to a pressurized gas orifice 28having a predetermined diameter. In one preferred embodiment, the gasinlet 22 is coaxial with the cylindrical middle portion 14 and extendsthrough the bottom wall 30 of the chamber 20.

A nozzle cover 32 is slideably mounted over the nozzle 26. As shown inFIGS. 4–5, the nozzle cover 32 is preferably a tapered tubular memberhaving openings at either end. The nozzle cover 32 slides over thenozzle 26 of the pressurized gas inlet 22 to form at least onepassageway 34 from an opening located near the bottom of the nozzlecover 32 to the top of the nozzle cover. In alternative embodiments, thepassageway may be formed by a spacing between the nozzle and nozzlecover, a groove 34 in the inner circumference of the nozzle cover, agroove in the outside of the nozzle, or a combination of grooves on theoutside of the nozzle and inside of the nozzle cover. A fluid outlet ispositioned adjacent the pressurized gas outlet 28. In one preferredembodiment, the fluid outlet 36 is an annular orifice defined by a gapbetween the inner diameter of the tip of the nozzle cover and the outerdiameter of the tip of the nozzle. The tip of the nozzle cover 32 mayinclude one or more stop pins 41 to limit the upward travel of thenozzle cover 32. Although a single annular orifice is shown, embodimentswhere the fluid outlet has other shapes, or comprises more than onediscrete orifice positioned adjacent the pressurized gas orifice, arealso contemplated. A fluid inlet 35 is preferably positioned at theopposite end of the nozzle cover 32. As shown in FIGS. 6–8, the fluidinlet is also an annular orifice and is defined by a gap between theinner diameter of the bottom of the nozzle cover 32 and the outerdiameter of the base of the nozzle 26.

An embodiment is also contemplated with fluid pathways that arecompletely enclosed within the thickness of the nozzle cover such as oneor more tunnels bored from, or molded in, the bottom of the nozzle coverextend some or all of the distance up to the opening at the top of thenozzle cover. Further, an alternative embodiment may consist of an arrayof one or more discrete tubes connected in a ring around the pressurizedgas outlet 28, where each of the tubes provides a passageway from thefluid reservoir 80 to a respective point adjacent the pressurized gasoutlet 28.

In the embodiment of FIGS. 1–8, the entire nozzle cover 32 is attachedto, or integrally molded with, an actuator piston 38. In one embodiment,the nozzle cover includes one or more integrally formed arms 40 thatconnect to the bottom portion 42 of the circumferential flange 44 of theactuator piston 38. Any number of arms 40 may be utilized.

A diverter 46 is preferably attached to, or integrally molded with, theinside of the nebulizer 10. As shown in FIG. 3, a support beam 48connects the diverter 46 to an inner cylindrical flange 60 in the middleportion 14 of the nebulizer. Preferably, the diverter 46 has a flatsurface having a predetermined area and is positioned at a fixeddistance h₁ from the gas orifice 28. In one preferred embodiment, h₁ isapproximately 0.75 millimeters (mm) and the width of the diverter isapproximately 4.5 mm. The surface is also preferably aligned parallel tothe surface of the tip of the nozzle 26 and perpendicular to the flow ofpressurized gas through the pressurized gas orifice 28.

Any of a number of configurations for fixing the position of thediverter with respect to the pressurized gas orifice are contemplated.For example, the cylindrical flange 160 may extend further into thechamber 120 so that the diverter 146 and support arm 148 are attached ormolded further from the bottom of the cylindrical flange 160 as shown inthe embodiment illustrated in FIG. 8. In FIG. 9, an embodiment is shownwhere the diverter 246 is attached to a support 248 directly connectedto the wall of the middle portion of the housing. A shorter cylindricalflange 260 provides clearance for the support 248. Alternatively, asshown in FIG. 10, the diverter 346 may be attached or molded to the lid311 of the nebulizer via an extension arm 348. In other alternativeembodiments, the diverter may be movable with respect to the pressurizedgas orifice or may be movable with the pressurized gas orifice such thatthe pressurized gas orifice and diverter move together independently ofthe fluid orifice. Another suitable diverter configuration is disclosedin U.S. Pat. No. 6,044,841, the entire disclosure of which isincorporated herein by reference.

Referring again to FIGS. 1–8, the upper portion 12 of the housing 13forms a cylindrical extension with an open proximal end 52 and apartially closed distal end 54. The distal end 54 has an annular ledge50 surrounding an opening 58 into the chamber 20. The annular ledge 50defines at least one air inlet opening 56 and preferably eight air inletopenings distributed along its circumference. Each air inlet opening 56is located toward the outer periphery of the distal end 54 of the upperportion 12 such that air outside of the nebulizer is primarily directedagainst an actuator piston 38 covering the air inlet opening 56 duringthe patient's initial inhalation. Preferably, the nebulizer isconfigured such that a gap exists between the air inlet opening and theactuator piston when the nebulizer is in a non-actuated state.

The opening 58 at the distal end 54 connects with a chimney, orcylindrical flange 60, extending down into the upper portion of thechamber 20. The cylindrical flange 60 is preferably of a diameter suitedto slideably receive the cylindrical extension 62 of the actuator piston38 that extends downward into the chamber 20. The cylindrical extension62 is positioned substantially coaxially within the cylindrical flange60 and acts as a vertical guide for the actuator piston 38. The openproximal end 52 of the upper portion 12 of the housing 13 has a diametersuited to receive the lid 11. The lid 11 may be threaded, snap-fit,friction-fit, molded or welded to the upper portion 12 of the housing13. The middle portion 14 of the housing 13 is preferably manufacturedof a clear plastic so that a caregiver can see the actuator piston anddetermine if the nebulizer is actuated.

The interior of the upper portion 12 is suited to slideably receive theactuator piston 38 and a relief piston 62, and to receive a biasingmeans 64 such as a plastic or metal spring. The actuator piston 38, asshown in FIGS. 2–3 and 6–8, includes an outer annular rib 66 with anouter diameter slightly less than the inner diameter of the upperportion 12 of the housing 13 to allow the actuator piston 38 to slide upand down within the upper portion 12. A center hole 68 is bounded by thecylindrical extension 62 that extends both down into the chamber 20through the opening 58 and, in the opposite direction, a short distanceinto the upper portion 12. At least one air inlet 72 is located in theactuator piston 38 adjacent to the center hole 68 that allows entrainedair received from air inlets 56 in the housing to travel through theactuator piston and against the underside of the relief piston 62. Asdescribed in more detail below, the negative pressure created above therelief piston 62 during inhalation preferably creates a force sufficientto move the relief piston 62 away from the actuator piston and allowsincreased air flow to the patient through openings 72 in the actuatorpiston 38. The actuator piston also includes at least one arm 40 orother structure connecting the nozzle cover 32 or part thereof to thebottom portion of the actuator piston cylindrical extension 62. The armcan be attached (i.e. friction fit, welded or glued), or integrallymolded to the extension 62.

Referring to FIGS. 2–3, the relief piston 62 also has an annular shapedefining a central opening 74. An inner annular rib 46 extends upwardfrom an inner diameter of the relief piston 62 and an outer annular rib78 extends upward from an outer diameter of the relief piston. Thecentral opening 74 has a diameter slightly larger than the portion ofthe cylindrical extension 62 extending up from the actuator piston'scenter hole 68. The outer diameter of the relief piston 62 is slightlyless than the inner diameter of the actuator piston's raised annular rib38 to allow the relief piston to slideably move between the ribs of theactuator piston. The outer diameter of the outer annular rib on therelief piston is also less than the inner diameter of the lid 11.Although the embodiment of FIGS. 2–3 illustrates a relief piston, inanother embodiment the nebulizer includes only the actuator piston andnot the relief piston.

A biasing means 64, such as a plastic or metal spring, is positionedadjacent the top of the relief piston 62. The biasing means 64 has apredetermined spring force that is designed to hold the pistons 38, 62down during an absence of inhalation, but that will be overcome oncesufficient negative pressure is created by a patient's inhalationeffort. In a preferred embodiment, one end of the biasing means 64 restsagainst the retainer lid 11 and the other end against relief piston 62between the inner and outer annular ribs 46, 78. Other biasing means,such as a flexible membrane or a set of oppositely charged magneticmaterials, may also be used. Additionally, the biasing means may consistof extra weights added to the relief piston and actuator piston, or theweight of the relief and actuator pistons by themselves, rather than aspring, so that gravity may be used to provide the necessary biasingforce keeping the pistons against the air inlets 56, 72 in a resting orexhalation position.

The bottom portion 16 of the housing 3 is used as a fluid reservoir 80.The fluid reservoir 80 preferably holds a fluid. In one embodiment, thefluid may comprise medication used to alleviate respiratory ailmentssuch as asthma and chronic obstructive pulmonary disease. The fluidreservoir 80 is bounded by a wall 30 that slopes down towards the bottomof the nozzle 26. Gravity urges the fluid in the reservoir toward thepassageway 34 defined by the nozzle and nozzle cover. Both thecylindrical middle portion 14 of the housing 13 and bottom portion 16 ofthe housing 13 are preferably constructed from a transparent plastic toallow a caregiver to monitor medication levels in the nebulizer. When ina nebulizing position, the passageway 34 guides the fluid from the fluidreservoir to the fluid outlet 36.

Various alternative fluid reservoirs can be used in the nebulizer 10.For example, as is disclosed in U.S. Pat. No. 5,823,179, the reservoirmay be formed of at least two portions: (1) an upper portion which isrelatively shallow and wide with a diameter approximately the same asthat of the chamber; and (2) a lower portion that is relatively narrow,but relatively deep. In this embodiment, the lower portion of thereservoir is wider than the outer diameter of the nozzle cover. Thisalternative embodiment can also be modified to include a thirdintermediate portion located between the upper and lower portions. Theentire disclosure of U.S. Pat. No. 5,823,179 is incorporated herein byreference.

Referring to FIGS. 6–8, the operation of the nebulizer is describedbelow. In the non-actuating state shown in FIG. 6, when a patient isexhaling or no longer inhaling, the biasing means 64 pushes against theinside of the lid 11 and down against the relief piston 62. The reliefpiston 62 presses against the actuator piston 38 which, in turn, keepsthe nozzle cover 32 a distance h₂ away from the diverter and against thenozzle 26. Thus, the fluid outlet 36 is positioned away from thepressurized gas orifice and, therefore, there is insufficient negativepressure to draw up the fluid from the reservoir through thepassageways.

Pressurized gas is continuously introduced into the chamber via thepressurized gas orifice 28 and is deflected radially outward from thegas orifice in a 360° pattern by the deflector 46. In the non-actuatedposition, the flow of gas fanning out over the annular fluid outlet isat a sufficient distance h₂ from the annular fluid outlet that nonebulization takes place. Additionally, the force of the biasing memberagainst the relief and actuator pistons closes the air inlets 72, 56 andkeeps air and any nebulized substance in the chamber 20 from escapingthrough the air inlets. In one embodiment, h₂ is approximately 2.0 mmwhen h₁, the fixed distance between diverter and nozzle, is 0.75 mm.Other ratios of h₂ and h₁ may be utilized to take into account changesin parameters such as the viscosity of the fluid in the reservoir andthe velocity of the pressurized gas entering the chamber.

When a patient begins inhaling through the air outlet 18, the force ofthe patient's inhalation lowers the pressure in the chamber and createsa negative pressure above the pistons causing both the actuator pistonand relief piston to simultaneously lift away from the annular wall ofthe upper portion of the housing. The nozzle cover 32, rigidly attachedto the actuator piston through the cylindrical extension and arms, movesup the pressurized gas nozzle until the fluid outlet reaches the lowpressure zone created by the continuous flow of gas diverted by thediverter. In order to maintain the fluid outlet at the appropriateposition during inhalation, upward movement of the actuator piston ispreferably limited by contact of the outer annular rib with the edge ofthe lid 11. Alternatively, other points of contact may be used to limitthe maximum upward movement of the nozzle and actuator piston. Forexample, the plurality of stops 41 on the upper edge of the nozzle cover32 shown in FIGS. 4 and 5 may be arranged around the perimeter of thetip of the nozzle cover so that motion of the nozzle cover is limitedwhen these stops contact the diverter.

In the nebulizing position (FIGS. 7 and 8) the low pressure zone createdover the annular fluid outlet by the gas fanning out against thedeflector and over the annular orifice, along with a capillary effect,draws the fluid from the reservoir 80 through the passageways 34 andinto the stream of pressurized gas. The fluid is aerosolized and drawnout through the air outlets 18 and a mouthpiece (not shown) into thepatient's respiratory system. After the nebulizer has already initiatednebulization of the fluid, and while the patient is continuing to inhaleand increase the negative pressure in the chamber, the relief pistonwill separate from the actuator piston thereby allowing more ambient airto be entrained in the cylinder and chamber. As illustrated in FIG. 7,the edge 15 of the lid 11 limits motion of the actuator piston 38, butthe smaller diameter relief piston 62 is not restricted by contact withthe edge of the lid and will separate from the actuator piston after theinitial period of the patient's inhalation.

Although nebulization has already started as soon as the actuator pistonhas lifted the nozzle cover to the appropriate spacing from thediverter, continued inhalation causes the relief piston to separate fromthe actuator piston. Separation of the relief piston from the actuatorpiston uncovers additional air inlets in the actuator piston and has theeffect of increasing air flow into the nebulizer and reducing theresistance to inhalation. FIG. 8 illustrates the flow path 71 of ambientair from outside the nebulizer through the inlets 56 in the housing 13and inlet 72 in the actuator piston 38. Ambient air continues down thecentral portion of the nebulizer through the cylindrical flange 60 andcylindrical extension 62 where nebulized fluid is gathered and drawnthrough the air outlet 18. In alternative embodiments, the upper portion12 of the housing may include internal protrusions or a flangepositioned to stop upward movement of the actuator piston and maintain aproper spacing between the annular orifice and the diverter duringnebulization. An advantage of the fixed diverter embodiment shown inFIGS. 1–8 is that the inhalation effort necessary to actuate thenebulizer is substantially unaffected by the force of the pressurizedgas impacting on the diverter.

Upon exhalation, the negative pressure in the chamber is replaced with apositive pressure such that the force of the biasing member against therelief and actuator pistons closes the air inlets and again moves thenozzle cover away from the low pressure zone generated by thepressurized gas inlet and diverter. Continued exhalation directs exhaledair through a relief valve on the mouthpiece (not shown) connected tothe air outlet to direct exhalation away from the nebulizer. Any of anumber of commonly available relief valves may be used with thepresently preferred embodiment. A suitable mouthpiece and relief valveare illustrated in U.S. Pat. No. 6,044,841, the entire specification ofwhich is incorporated herein by reference.

Although preferably operated by breath actuation, the nebulizer 10 mayalso be manually actuated. As shown in the embodiment of FIG. 11, thenebulizer 310 may include a manual actuating member 301 connected with,integral to, or capable of contact with the actuator piston 338 andextending out of the upper portion 312 of the housing 313 through an airinlet 356 or other opening. In FIG. 11, the manual actuating member 301is integrally formed with the actuator piston 338. The actuating member301 permits a caregiver or patient to move the actuator piston by hand,and thus move the nozzle cover, so that the nebulizer initiatesnebulization. Although the manually actuable nebulizer 310 isillustrated with a diverter that is integrally formed with the lid, anyof the other diverter or nozzle configurations disclosed herein, ortheir equivalents, may be used.

An alternative embodiment of a nebulizer 410 is illustrated in FIGS. 12and 13. Here, the nozzle cover consists of two portions. A first portion432A is fixed at the top of the gas nozzle 426 so that the pressurizedgas inlet 428, diverter 446 and annular orifice of the fluid outlet 436are all fixedly positioned with respect to one another at a spacingsuitable for nebulization. The second portion 432B is attached to theactuator piston with arms 440 and is moveable a predetermined distanceup and down the axis of the gas nozzle so that the annular orifice ofthe fluid inlet 435 moves with the actuator piston. As with the nozzlecover of the embodiment in FIGS. 1–8, one or more fluid pathways aredefined by spacing between the gas nozzle and nozzle cover, grooves inthe nozzle cover, grooves in the gas nozzle, or a combination of theseoptions.

In the non-actuating position, the second portion 432B is separate fromthe first portion 432A such that a gap 433 of a predetermined distanceexists between the two portions as shown in FIG. 12. As a result of thegap, the first portion 432A of the nozzle cover does not contact thefluid reservoir and there is no continuous fluid pathway between thefluid orifices, in other words no pathway from the reservoir and fluidinlet 435 to the fluid outlet 436, so that no fluid may reach the fluidoutlet. In the actuating position, the second portion is moved up untilit mates or abuts with the first portion as shown in FIG. 13. The twoportions 432A, 432B cooperate to form at least one continuous fluidpathway between the fluid outlet and the reservoir. The continuous fluidpathway permits the negative pressure over the fluid outlet to drawfluid from the reservoir and initiate nebulization. Similar to theembodiment of FIGS. 1–8, the embodiment of FIGS. 12–13 may utilize boththe actuator and relief pistons, or it may only include the actuatorpiston.

Another alternative embodiment of the nebulizer is illustrated in FIGS.14–16. In this embodiment, the nozzle cover has a fixed first portion532A and a movable second portion 532B. The first portion 532A is fixedat the top of the gas nozzle 526 so that the pressurized gas inlet 528,diverter 546 and annular fluid outlet 536 are all fixedly positionedwith respect to one another at a spacing suitable for nebulization.Preferably, the diverter 546 is connected with, or integrally formedwith a portion of the housing 513 or a chimney insert 501 connected withthe housing 513.

Unlike the embodiment of FIGS. 12 and 13, the nebulizer 510 is in theactuated position when the two portions 532A, 532B are separated.Preferably, the first portion 532A extends down into the reservoir anddefines at least one fluid pathway to the annular orifice. The secondportion 532B defines a collar for blocking the fluid inlet 535 at thefirst portion 532A. In one embodiment, the fluid inlet 535 may be anannular orifice defined by the space between the first portion and thegas nozzle 526. In another embodiment, the fluid inlet 535 may be one ormore separate fluid openings that are part of, or connected to, the baseof the first portion 532A. Preferably, the second portion is movablebetween a first position where any fluid pathway is substantially shutoff and a second position where the fluid inlet is open and the fluidpathway is open. When the nebulizer is in the non-actuated state (FIG.15), the second portion abuts, or mates with, the first portion. In theactuated position (FIG. 16), the second portion 532B is separated fromthe first portion 532A and nebulization can occur.

In order to achieve the separation of the first and second portions532A, 532B, movement of the actuator 538 and relief 562 pistons shouldbe opposite that of the actuator and relief pistons illustrated in theembodiment of FIGS. 1–8. Specifically, the pistons should move from thetop of the nebulizer toward the bottom during inhalation so that thesecond portion of the nozzle cover will move down and away from thefirst portion. As shown in FIGS. 14–16, the nebulizer 510 has the reliefpiston 562 coaxially positioned around a portion of the actuator piston538. A biasing member 564 holds the actuator and relief pistons 538, 562against the lid 511 so that the air inlets 556 in the lid 511 arecovered by the pistons. The lid 511 mates with the chimney insert 501connected to the housing 513, and the upper portion of the chimneyinsert 501 provides a ledge that limits the downward movement of theactuator piston 538 after a patient begins to inhale and actuates thenebulizer (see FIG. 16). Thus, when the patient inhales through themouth piece 561, a negative pressure pulls both the actuator and reliefpistons down and moves the second portion of the nozzle cover 532B topermit fluid to reach both fluid orifices (i.e. the fluid inlet 535 andthe fluid outlet 536).

Additional inhalation draws the relief piston 562 away from the actuatorpiston 538 so that air from the inlets 556 can also flow throughopenings 572 in the actuator piston and relieves the inhalation effort.Upon exhalation, the biasing member force returns the pistons 538, 562to a non-nebulizing position and exhaled air is directed through aone-way valve 563 in the mouthpiece 561. This embodiment of thenebulizer may also be manually actuated by pressing down on a manualactuator 557 extending through a central opening 559 in the lid 511. Onesuitable nebulizer piston configuration is illustrated in U.S. Pat. No.6,044,841, the entire disclosure of which is incorporated herein byreference. In similar fashion, the downward moving piston configurationmay be used with a nozzle cover that is suspended above, or against, thediverter so that inhalation effort would move the actuator piston andattached nozzle cover down to complete the fluid pathway and place thefluid orifice in the low pressure zone created by the continuous flow ofpressurized gas against the diverter. All or a portion of the nozzlecover may be connected with the actuator piston in this downward pistonmotion alternative embodiment.

Another alternative embodiment of the nebulizer is illustrated in FIGS.17 and 18. In this embodiment, the nebulizer 610 has a housing with ahorizontal section 612 and a vertical section 614. The horizontalsection has an air inlet 616 for receiving a supply of air and an airoutlet 618 where a patient inhales nebulized fluid. The vertical section614 defines a fluid reservoir 620 for holding the fluid. A pressurizedgas inlet 622 extends into the chamber 624 through the bottom portion ofthe vertical section 614. Inside the chamber 624, the pressurized gasinlet 622 forms a nozzle 626 that tapers down to a pressurized gasorifice 628 positioned opposite a diverter 646. The diverter 646 ispreferably fixedly positioned by support arms 647 to the housing andmaintained at a fixed distance from the gas orifice. As shown, thediverter is attached to a fixed portion 632A of the nozzle cover. Thefixed portion 632A of the nozzle cover is attached to the verticalsection 614 by one or more nozzle cover supports 633. The fixed portionof the nozzle cover defines a fluid inlet 635, which may comprise one ormore openings near the bottom of the reservoir 620, and defines a fluidoutlet 636, which may be an annular orifice, with the tip of thepressurized gas nozzle 626.

As illustrated in FIG. 17, a movable portion 632B of the nozzle cover isconnected by arms 640 to a vane 638 pivotally attached with an axle 642mounted in a bracket on the horizontal section 612 of the nebulizer 610.A biasing member, such as a torsion spring 644 positioned on the axle642, urges the movable portion 632B of the nozzle cover away from thepressurized gas nozzle 626 so that, at rest or during exhalation, thereis a gap 648 that prevents fluid from reaching the fluid outlet 636.Accordingly, as illustrated in FIG. 16, no nebulization takes placeduring exhalation when the movable portion of the nozzle cover is heldaway from the fixed portion and the pressurized gas nozzle. When apatient inhales at the outlet 618, the flow of air through thehorizontal section 612 draws the vane toward the air outlet 618. Themovable portion 632B of the nozzle cover pivots with the vane 638 andcovers the gap 648 so that a complete fluid path is formed between thefluid orifices from the fluid inlet 635 at the reservoir 620 to thefluid outlet 636 as shown in FIG. 17. As explained above for the otherembodiments, the continuous flow of pressurized gas from the pressurizedgas orifice against the fixed diverter 646 creates a low pressure regionabove the fluid outlet so that fluid is drawn up along the fluidpathway, or pathways, between the nozzle cover and nozzle. This fluid isthen nebulized in the pressurized gas flow.

Illustrated in FIGS. 19 and 20 is an alternative embodiment of the vaneand nozzle cover assembly for use with the housing having the horizontal612 and vertical 614 sections as shown in FIGS. 17 and 18. The nozzlecover 650 is movably mounted relative to the gas nozzle 652. The gasnozzle is preferably attached to the vertical section 614 of thenebulizer. A pair of arms 654 attached to the nozzle cover 650 arelinked to rocker arms 656 at linkage points 658. The rocker arms 656 areattached to an axle 660 that pivots about its axis in response tomovement of a vane 662. The vane 662 is also attached to the axle 660.The axle 660 is preferably rotatably mounted in the wall of the verticalor horizontal section of the nebulizer.

FIG. 19 shows the vane 662 and nozzle cover 650 in a non-actuatedposition. In the non-actuated position, the nozzle cover 650 is helddown against the gas nozzle 652 such that the fluid outlet 664 ispositioned away from the low pressure region created by the flow ofpressurized gas from the pressurized gas orifice 666 against thediverter 668. The diverter 668 is preferably attached to a support 670that is fixedly attached to the housing of the nebulizer. Alternatively,and/or additionally, the nozzle cover 650 may be configured tosufficiently close off the fluid inlet 667 so that substantially nofluid may flow into the fluid passage or passages (not shown) betweenthe fluid orifices (inlet 667 and outlet 664) when the nebulizer is inthe non-actuated position. The weight of the nozzle cover 650, or thebiasing force applied by a biasing member such as a spring, may keep thenozzle cover in the non-actuated position at rest and during exhalation.

Referring to FIG. 20, when a patient inhales through the nebulizer, theflow of inhaled air causes the vane to move. The vane moves by pivotingabout the axis of the axle. The movement of the axle causes the rockerarms to lift up the nozzle cover via the linkage points 658 and arms654. The movement of the nozzle cover moves the location of the fluidoutlet 664 to a desired position relative to the diverter 668 such thatfluid may be drawn up through the fluid inlet 667 from the fluidreservoir along the one or more fluid pathways. Various types of stops(not shown) may be used to limit the movement of the nozzle cover afterit reaches the actuating position. For example, as discussed previously,protrusions may be fabricated, or attached, to the top of the nozzlecover keep the proper spacing between the nozzle cover and diverterduring actuation. Alternatively, one or more stops may be fabricated, orattached, to the interior of the nebulizer such that the vane 662 cannotpivot about the axle any farther than the optimum actuation position.

In alternative embodiments, the vane 638, 662 may be constructed of aflexible material that is configured to flex with a patients inhalationand exhalation rather than pivoting about a point. Also, differentportions of the nozzle and/or nozzle cover may be movably mounted toswing with the vane and form the fluid pathway or a fluid orifice duringinhalation. Further, a movable collar may be used to block the fluidinlet 667 or outlet 664 in another alternative configuration capable ofactuating the nebulizer in coordination with a patient's breathing.

In the embodiment of FIGS. 21–27, a nebulizer 710 is shown with a reliefpiston 762 separately mounted to the lid 711 and the actuator pistonslidably movable between the lid 711 and the inner cylindrical flange760 in the central portion 714 of the housing. A diverter 746 isconnected to the lower portion of the inner cylindrical flange 760 andmaintained at a fixed distance from the pressurized gas orifice 728 onthe pressurized gas inlet 726. A nozzle cover 732 is attached to theactuator piston 738 by arms 740 integrally formed with the nozzle cover.A bottom portion 716 of the nebulizer 710 defines a fluid reservoir 780for holding a fluid to be nebulized. As shown in FIGS. 21–23, the bottomportion 716 may be threadably attached to the middle portion 714 of thenebulizer.

In operation, the nebulizer 710 is in a non-actuated state when at rest(FIG. 23) or during a patient's exhalation, and in an actuated stateduring a patient's inhalation (FIG. 21). Referring to FIGS. 22 and 24,when a patient inhales through the mouthpiece 761 and draws air from thechamber 720, ambient air is pulled through the air inlets 756 in themiddle portion 714 of the housing and into a chamber 772 between theoutside surface 768 of the actuator piston 738 and the inside surface770 of the middle portion 714 of the housing. The ambient air is thendrawn up over the lip 766 of the actuator piston, down between the innersurface 778 of the actuator piston and the inner extension 746 of thelid 711, and into the chamber 720 as shown by flow arrows 771. As bestshown in FIG. 23, this air flow raises the actuator piston 738 up andmoves the nozzle cover 732 up so that the fluid outlet 736 is raised toa nebulizing position and the fluid pathways 734 defined between thenozzle cover 732 and the pressurized gas nozzle 726, or the fluid inlet735, are not interrupted. Once the nozzle cover has moved to theactuated position, shown in FIG. 23, the fluid in the fluid reservoir780 is drawn into the fluid inlet 735, up the fluid pathway and out thefluid outlet 736, entrained against the fixed diverter 746 andaerosolized. As inhalation continues to increase the negative pressurein the chamber, the relief piston 762 will begin to open and allow moreambient air in through openings 763 in the lid.

Upon exhalation, the relief piston 762 will shut the openings in the lidto restore the original pressure in the housing. The actuator piston 738will lower to its rest position and move the fluid outlet away from thelow pressure zone created by the pressurized gas impacting the fixeddiverter 746. Any air exhaled by the patient will preferably passthrough a one-way valve 763 on the mouthpiece 761 and not enter the airoutlet 718 of the nebulizer. Although the air inlets 756 are shownunderneath the periphery of the middle portion 714 in FIGS. 21 and 24,the air inlets can be located in any position that will expose theoutside surface 768 of the actuator piston 738 to ambient air.Additionally, in order to increase the performance of the nebulizer inlow pressure/low flow situations, the area of the outside surface 768exposed to ambient air may be increased.

In one preferred embodiment, if the continuous pressurized gas flow intothe chamber 720 from the pressurized gas inlet 728 is at a rate of 8Liters/minute (L/min), the actuator piston 738 will respond to theinhalation once the inhalation rate exceeds the 8 L/min and generates anegative pressure in the range of 0.5 to 1.0 centimeters H₂O.Nebulization should begin once the initial inhalation has moved theactuator piston up into the actuation position. The force initiallykeeping the actuator piston in the non-actuated state may be the weightof the actuator piston or may be supplied by any of a number of biasingmembers. As the patient continues inhaling and the negative pressureincreases to approximately 1.0 centimeters H₂O, the relief piston 762opens. The relief piston is preferably configured to increase the amountof additional ambient air provided to the chamber as the patient'sinhalation increases to keep the negative pressure from rising to apoint that makes inhalation difficult for the patient.

As best shown in FIGS. 28 and 29, The pressurized gas nozzle 726 andnozzle cover are shaped such that movement of the nozzle cover 732 froman actuated position (FIG. 28) to a non-actuated position (FIG. 29) bothmoves the fluid outlet away from the low pressure zone created by thegas flow diverted by the fixed diverter 746 and quickly cuts off thefluid pathways 734. When the nebulizer is actuated, a supply of fluid issteadily drawn up the fluid pathways 734 and provided at the fluidoutlet. In order to avoid rapidly forcing excess fluid remaining in thefluid pathway out of the fluid outlet when the nozzle cover is moved tothe non-actuated position, the upper portion of the nozzle 726 isfabricated with a cut-off region that cooperates with the inner diameterof the upper end of the nozzle cover to quickly cut off the fluidpathways. The cut-off region may simply be an area 797 of increaseddiameter close to the tip of the nozzle that fits tightly against thenozzle cover. In this manner, only a limited amount of fluid remainingin the extreme upper section 798 of the fluid pathway 734 will bedisplaced.

Referring to FIG. 25, the relief piston 762 preferably consists of aflexible material 790 covering the openings 763 in the lid 711. Theflexible material, which may be constructed from plastic, metal or othersuitably flexible substance, is captured by a central post 792 integralwith the lid and pre-loaded against a ridge 791 so that the reliefpiston will not open until a desired negative pressure is reached in thechamber of the nebulizer. Another embodiment of the relief piston 793 isillustrated in FIG. 26. In this embodiment, the relief piston 793consists of a rigid valve 794 biased against the ridge 791 to cover theopenings 763 in the lid 711. A biasing member 795, such as a metal leafspring, pre-loads the rigid valve against the ridge 791. The rigid valvemay be made of any rigid material, such as polypropylene. In operation,the rigid valve 794 slides up and down the post 796 extending from thelid 711. The biasing member 795 may be mounted on the post 796 using anyof a number of techniques, including friction fit, heat staking and soon.

The embodiments of FIGS. 21–27 include some additional features forimproving the flexibility and performance of the nebulizer. For example,referring to FIGS. 21 and 23, an embodiment of the reservoir 780 isillustrated where the interior of the sloped lower wall 730 defining thereservoir is lined with a plurality of vertical ribs 788. The ribs 788may cover all, or a portion, of the inside of the lower wall 730 andpreferably extend up to the top of the lower portion 716 of the housing.Occasionally, fluid that is to be nebulized will collect on the wall ofthe reservoir due to condensation effects and from larger nebulizedparticles impacting against the wall. This fluid will typically onlydrop back into the main pool of fluid in the reservoir when theparticles become large enough so that the force of gravity can overcomethe surface tension keeping them stuck to the walls. The ribs 788 definecorresponding vertical grooves or channels 789 that can assist inallowing droplets to more rapidly return to the pool of fluid in thereservoir. The sharp angle of the ribs preferably keep droplets fromforming on the tips of the ribs so that there is less area for dropletsto attach. The ribs 788 may help to direct the droplets into thechannels 789 where the droplets may accumulate more quickly and fallback into the reservoir. Although the ribs disclosed in FIGS. 21–27 areshown as triangular in cross-section, other rib shapes such assemicircles, rectangles and other shapes, may be fabricated.Additionally, a variety of differently shaped ribs and channels may becombined.

Another aspect of the nebulizer shown in FIGS. 21–27 is the continuousnebulization selection lever 782. The lever 782 is rotatably mounted ina chamber 786 on the middle portion 714 of the housing. The leverincludes a threaded portion 784 positioned to engage the upper lip 766of the actuator piston 738. The lever 782 may be manually rotated toallow the nebulizer 710 to operate in a breath actuated mode or acontinuous nebulization mode. In the breath-actuated mode, the threadedportion 784 of the lever 782 does not contact the upper lip 766 of theactuator piston 738 so that the actuator piston may freely operate inthe manner previously described. As shown in FIG. 27, when the lever isrotated to put the nebulizer in continuous nebulization mode, thethreaded portion 784 holds the actuator piston by the upper lip 766 sothat the actuator piston, and attached nozzle cover, are in the actuatedposition and continuously nebulize any fluid in the reservoir. Althougha horizontally rotatable lever 782 is shown, other two position switchesor mechanisms, may be used.

Another embodiment of a breath-actuated nebulizer 800 is illustrated inFIGS. 30–32. The nebulizer 800 of FIGS. 30–32 is substantially similarto the embodiment illustrated in FIGS. 21–24 with the exception of thegas nozzle 826 and nozzle cover 832 configuration. The nozzle cover 832defines an exit port 836 aligned with the pressurized gas orifice 828 inthe nozzle 826. The diameter of the exit port 836 is preferably smallerthan the outer diameter of the top portion 827 of the nozzle 826. In theactuated position, as shown in FIG. 31, the actuator piston 838 (FIG.30) lifts the nozzle cover 832 so that a gap 829 is maintained betweenthe top portion 827 of the nozzle 826 and the underside 830 of the topof the nozzle cover 832. The pressurized gas that is continuously fedthrough the nozzle 826 can then draw fluid from the reservoir 880through the fluid pathway 834. The gas and fluid interact in the gap 829and form an aerosol before exiting the exit port 836 in the nozzle cover832. The aerosol then exits through the exit port where it is entrainedagainst a diverter 846 to diverter out larger particles in the aerosolflow that was created in the gap 829 underneath the nozzle cover.Preferably, the diverter 846 is fixedly positioned in the nebulizer 800.In alternative embodiments, the diverter may be attached to the nozzlecover so as to maintain a constant distance between the exit port andthe diverter, or the diverter may be movable independently of themovable nozzle cover.

During exhalation, or at rest, the actuator piston 838 lowers the nozzlecover 832 until the underside 830 of the top of the nozzle cover 832rests against the top portion 827 of the nozzle 826. Althoughpressurized gas may still flow freely, the fluid pathway 834 is blockedoff and fluid cannot be drawn from the reservoir 880. Thus, the gasnozzle 826 and nozzle cover 832 in FIGS. 30–32 are arranged in aninternal mixing configuration such that the pressurized gas flowinteracts with the fluid from the fluid pathway, or pathways, prior toleaving the exit port 836 in the nozzle cover 832. In contrast, theembodiment of FIGS. 21–24 illustrates an external mixing arrangementwhere the gas and fluid only interact outside of the nozzle and nozzlecover configuration and utilize a diverter to enhance the interactionbetween the gas and the fluid to promote formation of an aerosol.Additionally, or alternatively, the fluid inlet 835 at the base of thenozzle cover may be used to control fluid flow to the top of the nozzlein coordination with a patient's breathing. As discussed in the previousembodiments, the nozzle cover 832 movement can be used to press thefluid inlet 835 against the reservoir 880 wall or to move a collar thatblocks off the fluid inlet 835.

The invention may be embodied in other forms than those specificallydisclosed herein without departing from its spirit or essentialcharacteristics. The described embodiments are to be considered in allrespects only as illustrative and not restrictive, and the scope of theinvention is intended to be commensurate with the appended claims.

1. A nebulizer for generating an aerosol for delivery to a patient, the nebulizer comprising: a housing having an air inlet, a chamber for holding the aerosol and a fluid reservoir; an air outlet communicating with the chamber for permitting the aerosol to be withdrawn from the chamber; a nozzle located in the chamber; a fluid orifice defined by an outer diameter of the nozzle and an inner diameter of an end of a nozzle cover, wherein at least a portion of the nozzle cover is moveable with respect to the nozzle; a diverter positioned in the chamber adjacent to the nozzle and the fluid orifice; and an operational mode switch operatively connected with the nozzle cover, the operational mode switch having a breath actuation position, wherein the nozzle cover moves in response to a patient's breathing, and a continuous nebulization position, wherein the nozzle cover is immobilized and the fluid reservoir is in continuous communication with the fluid orifice.
 2. The nebulizer of claim 1, wherein the diverter is in a fixed position relative to the nozzle.
 3. The nebulizer of claim 2, wherein the nozzle cover comprises a fixed portion and a movable portion.
 4. The nebulizer of claim 3, wherein, when the operational mode switch is in the breath actuated position, the fixed portion of the nozzle cover and the nozzle define a first portion of a fluid pathway between the fluid orifice and the fluid reservoir, and the movable portion of the nozzle cover and the nozzle define a second portion of the fluid pathway between the fluid orifice and the fluid reservoir in response to an inhalation.
 5. The nebulizer of claim 2, wherein the nozzle cover is positioned substantially coaxially about the nozzle.
 6. The nebulizer of claim 2, wherein the diverter is connected with a wall of the housing.
 7. The nebulizer of claim 6, wherein the diverter and the wall of the housing comprise a single piece of material.
 8. The nebulizer of claim 1, wherein the at least a portion of the nozzle cover comprises an entirety of the nozzle cover.
 9. The nebulizer of claim 1, wherein the operational mode switch extends outside of the housing of the nebulizer.
 10. The nebulizer of claim 9, wherein the operational mode switch comprises a lever.
 11. The nebulizer of claim 9, wherein the operational mode switch is in contact with an actuator piston, and wherein the actuator piston is attached to the nozzle cover.
 12. The nebulizer of claim 1 further comprising a mouthpiece removably attachable with the air outlet, the mouthpiece comprising a one-way exhalation valve configured to vent air exhaled into the mouthpiece.
 13. The nebulizer of claim 1, wherein the diverter is positioned to divert a gas passing through the nozzle over the fluid orifice.
 14. A nebulizer for generating an aerosol for delivery to a patient, the nebulizer comprising: a housing having an air inlet and a chamber for holding the aerosol; an air outlet communicating with the chamber for permitting the aerosol to be withdrawn from the chamber; a nozzle located in the chamber; a nozzle cover positioned adjacent the nozzle and coaxially moveable relative to the nozzle, wherein a fluid orifice is defined by an inner diameter of an end of the nozzle cover and an outer diameter of the nozzle; a diverter positioned in the chamber adjacent to the nozzle and fluid orifice; and means for selecting an operational mode of the nebulizer, wherein in a first operational mode, the nozzle cover moves in response to a patient's breathing such that nebulization ceases during an exhalation, and in a second operational mode, the nebulizer is configured to provide continuous nebulization.
 15. The nebulizer of claim 14, wherein the means for selecting the operational mode is manually adjustable between the first and second operational modes.
 16. The nebulizer of claim 15, wherein the air inlet comprises a one-way valve responsive to an increase in negative pressure over an initial negative pressure to permit additional ambient air into the chamber.
 17. The nebulizer of claim 14, wherein the diverter is configured to divert a gas issuing from the nozzle over the fluid orifice. 